Increased Breast Meat Yield Research Articles

A microbial muramidase improves growth performance and reduces inflammatory cell infiltration in the intestine of broilers chickens under Eimeria and Clostridium perfringens challenge

The objective of the present studies was to evaluate muramidase (MUR) supplementation in broilers under Eimeria and/or Clostridium perfringens challenge. For this, 2 experiments were conducted. Experiment 1. A total of 256 one-day old male Cobb 500 chicks were placed in battery cages in a completely randomized design, with 5 treatment groups, 7 replicate cages per treatment and 8 birds per cage. The treatments were: nonchallenged control (NC), challenged control (CC), CC+MUR at 25,000 or 35,000 LSU(F)/kg, and CC+Enramycin at 10 ppm (positive control-PC). Challenge consisted of 15× the recommended dose of coccidiosis vaccine at placement, and Clostridium perfringens (108 CFU/bird) inoculation at 10, 11, and 12 d. Macro and microscopic evaluation, immunohistochemistry, and gene expression were evaluated at 7, 14, 21, and 28 d of age. Experiment 2. A total of 1,120 one-day old male Cobb 500 chicks were placed in floor pens with fresh litter in a completely randomized design, with 4 treatment groups, 8 replicate pens per treatment, and 35 birds per pen. The treatments were: Control, supplementation of MUR at 25,000 or 45,000 LSU(F)/kg, and a positive control (basal diet plus Enramycin). At 10, 11, and 12 d of the experiment all the birds were inoculated by oral gavage with a fresh broth culture of a field isolate Clostridium perfringens (0.5 mL containing 106 CFU/bird). It was observed that in Experiment 1 MUR supplementation reduced the infiltration of macrophages and CD8+ lymphocytes in the liver and ileum of infected birds, downregulated IL-8 and upregulated IL-10 expression. In Experiment 2, MUR linearly improved the growth performance of the birds, increased breast meat yield, and improved absorption capacity. MUR supplementation elicited an anti-inflammatory response in birds undergoing a NE challenge model that may explain the improved growth performance of supplemented birds.

Reducing dietary crude protein in broiler diets does not compromise performance and reduces environmental impacts, independently from the amino acid density of the diet

The objective of the present experiment was to investigate the influence of dietary CP, standardized ileal digestible ( SID) Lys level and their interaction in male Ross 308 broilers. From day 10, six experimental treatments were tested until day 35. The six experimental treatments consisted in a 3 × 2 factorial design with 3 levels of dietary SID Lys/CP (equaivalent to 3 levels of dietary CP) and 2 levels of dietary SID Lys. Growth performance, uniformity, carcass traits, litter quality, blood & gut parameters, nitrogen ( N ) emissions and global warming potential ( GWP ) were measured or calculated. There was no interaction for all criteria except for NH 3 and N 2 O volatilization. The increase of dietary SID Lys/CP did not affect growth performance or uniformity, increased abdominal fat yield, decreased all N related parameters (litter N, blood uric acid, N excretion, NH 3 and N 2 0 volatilization). There was an interaction between dietary CP and AA origin for GWP; GWP was further reduced after CP reduction when using AA from EU. Increasing SID Lys improved growth performance, increased uniformity, increased breast meat yield, reduced abdominal fat yield, but increased N emissions and GWP. This study indicates that dietary CP can be drastically reduced in different nutritional contexts without negatively affecting growth performance, and with positive benefits on the environment.

Dietary branched-chain amino acid assessment in broilers from 22 to 35\u2009days of age

BackgroundValine and isoleucine are similar in chemical structure and their limitation in broiler chicken diets. To evaluate their limitation and interactive effects, multivariate assessment nutrition studies for the branched-chain amino acids (BCAA) are needed. A three level (− 1, 0, + 1), three-factor Box-Behnken design study was conducted to assess dietary BCAA ratios to lysine of 65, 75, and 85 for valine, 58, 66, and 74 for isoleucine, and 110, 130, and 150 for leucine in male and female Lohman Indian River broilers from 22 to 35 d of age.ResultsLive performance of male broilers was not affected by BCAA level. However, male broilers fed increasing isoleucine had improved (P = 0.07) carcass yield as leucine and valine were reduced. Female broilers had improved body weight gain (P = 0.05) and feed conversion (P = 0.003) when leucine and isoleucine were at their lowest levels, independent of valine, but increasing leucine impaired live performance and warranted concomitant increases in isoleucine to restore responses. Increasing dietary isoleucine and valine in female broilers increased breast meat yield (P = 0.05), but increasing leucine tended to diminish the response.ConclusionThe female Lohman Indian River broiler is more sensitive to BCAA diet manipulation than males. Specifically, as dietary leucine is increased in female broilers, dietary isoleucine increases were needed to offset the negative effects. Both increases in dietary valine and isoleucine improved breast meat yield in female broilers, but only when birds were fed the lowest dietary leucine.

Performance, meat quality, and pectoral myopathies of broilers fed either corn or sorghum based diets supplemented with guanidinoacetic acid

One experiment was conducted to evaluate the effects of guanidinoacetic acid (GAA) supplementation in broilers fed corn or sorghum-based diets on live performance, carcass and cut up yields, meat quality, and pectoral myopathies. The treatments consisted of corn or sorghum-based diets with or without the addition of GAA (600g/ton). A total of 800 one-d-old male Ross 708 broiler chicks were randomly placed in 40 floor pens with 10 replicates (20 birds per pen) per each of the four treatments. At hatch, 14, 35, and 50 d, BW and feed intake were recorded. BW gain and FCR were calculated at the end of each phase. Four broilers per pen were selected and slaughtered at 51d and 55d of age to determine carcass and cut up yields, meat quality and myopathies (spaghetti muscle, white striping, and wooden breast) severity in the Pectoralis major. Data were analyzed as a randomized complete block design in a 2 × 2 factorial arrangement with grain type and GAA supplementation as main effects. At 50 d, diets containing GAA improved (P < 0.01) FCR (1.682vs. 1.724 g:g) independently of grain type. At 55 d, broilers fed corn diets with GAA had higher breast meat yield (P < 0.05) compared to corn without GAA. Drip and cook loss, and shear force (Warner-Bratzler) were not affected (P > 0.05) by GAA supplementation at any slaughter ages. However, GAA decreased (P < 0.05) the ultimate pH at 51 and 55 d in breast meat samples compared to unsupplemented diets. At 51 d, broilers supplemented with GAA had double (P < 0.05) breast meat fillets without wooden breast (score 1) compared with broilers fed non-supplemented diets, therefore reducing the severity of this myopathy. In conclusion, GAA supplementation improved broiler live performance in broilers raised up to 50 d independently of grain source, increased breast meat yield in corn-based diets and reduced the severity of wooden breast myopathy.

Selection response and estimation of the genetic parameters for multidimensional measured breast meat yield related traits in a long-term breeding Pekin duck line.

ObjectiveThis study was conducted to estimate the genetic parameters and breeding values of breast meat related traits of Pekin ducks. Selection response was also determined by using ultrasound breast muscle thickness (BMT) measurements in combination with bosom breadth (BB) and keel length (KL) values.MethodsThe traits analyzed were breast meat weight (BMW), body weight (BW), breast meat percentage (BMP) and the three parameters of breast meat (BB, KL, and BMT). These measurements were derived from studying 15,781 Pekin ducks selected from 10 generations based on breast meat weight. Genetic parameters and breeding value were estimated for the analysis of the breeding process.ResultsEstimated heritability of BMW and BMP were moderate (0.23 and 0.16, respectively), and heritability of BW was high (0.48). Other traits such as BB, KL, and BMT indicated moderate heritability ranging between 0.11 and 0.28. Significant phenotypic correlations of BMW with BW and BMP were discovered (p<0.05), and genetic correlations of BMW with BW and BMP were positive and high (0.83 and 0.66, respectively). It was noted that BMW had positive correlations with all the other traits. Generational average estimated breeding values of all traits increased substantially over the course of selection, which demonstrated that the ducks responded efficiently to increased breast meat yield after 10 generations of breeding.ConclusionThe results indicated that duck BMW had the potential to be increased through genetic selection with positive effects on BW and BMP. The ultrasound BMT, in combination with the measurement of BB and KL, is shown to be essential and effective in the process of high breast meat yield duck breeding.

Reconsidering betaine as a natural anti-heat stress agent in poultry industry: a review

Betaine is found ubiquitously in plants, animals, microorganisms, and rich dietary sources including seafood, spinach, and wheat bran. The chief physiological role of betaine is to function as a methyl donor and an osmolyte. Betaine also acts as an osmolyte,to maintain the avian's cellular water and ion balance to improve the avian's capacity against heat stress via preventing dehydration and osmotic inactivation. It helps in maintaining the protective osmolytic activity, especially in heat-stressed birds. Betaine may promote various intestinal microbes against osmotic variations and thus improve microbial fermentation activity. Previous studies showed that dietary supplementation of betaine in poultry diets could positively affect nutrients' digestibility, reduce abdominal fat weight, and increase breast meat yield. In addition, betaine has been reported to protect internal organs and boost their performance. Its inclusion in poultry diet is sparing essential amino acids like choline and methionine. In addition, it may play an important role in lean meat production by positively affecting the lipid metabolism with increased fatty acids catabolism and thus reducing carcass fat deposition. The aim of this review article was to broaden the knowledge regarding betaine and its importance in the poultry industry to cope with the heat stress problem. Moreover, it should be added to the diet as a natural anti-stressor through different routes (water/feed) to overcome the heat stress problem. However, further studies need to be conducted at the genetic and molecular basis to elucidate the mechanism behind the betaine as a natural anti-heat agent to decrease the heat stress problem in the poultry industry.

Effects of Guanidinoacetic Acid Supplementation to Broiler Diets With Varying Energy Content

An experiment was conducted to determine the response of broiler chickens to guanidinoacetic acid (GAA) added to diets with different energy levels during fattening to 35 days of age. Ross 308 male chicks were allotted to 10 treatments, each consisting of six replicates of 140 birds/pen. Five maize-soyabean meal isonitrogenous diets with decreasing AMEn levels (100, 99, 98, 97 and 96% of requirement) with or without supplements of 0.6 g/kg CreAMINO® containing a minimum of 96% GAA were formulated. The criteria of response were feed intake, body weight gains, feed conversion ratio and carcass, breast meat, leg meat and abdominal fat yields. Supplementation of broiler diets with 0.06% GAA resulted in a significant (P < 0.05) decrease in voluntary feed intake. With decreasing AMEn level, voluntary feed intake and consequently protein and amino acid intakes increased which was manifested by improved growth performance (P < 0.01). GAA supplements significantly (P < 0.001) improved feed conversion ratio and efficiency of AMEn utilization and significantly (P < 0.01) increased breast meat yield. With decreasing AMEn level, the effects of GAA supplementation tended to diminish.

Efficacy of dimethylglycine as a feed additive to improve broiler production

Dimethylglycine (DMG) is a naturally occurring glycine derivative, which is useful as additive to broiler diets as it improves nutrient digestibility and reduces the development of broiler ascites syndrome. This study evaluated the efficacy of dietary DMG to enhance performance of broiler chickens. Three trials were conducted to evaluate the effect of dietary supplementation with 1g Na DMG/kg on growth performance and carcass characteristics. In Trial 1, the effect of sex was also assessed in a 2×2 factorial arrangement of treatments. In Trials 1 (Germany), 2 (Austria), and 3 (Italy), each treatment consisted of 6, 12, and 11 replicate pens with 20, 15, and 16 one-day-old broiler chickens per pen, respectively. Dietary DMG supplementation resulted in improved feed conversion ratio (FCR) in the starter phase by 8.8% (P=0.004), 6.4% (P=0.001), and 4.8% (P=0.006) compared with the control diet in Trials 1, 2, and 3, respectively. The overall FCR improved in broiler chickens fed the diets supplemented with DMG by 3.8% and 4.1% in Trials 1 (P=0.007) and 3 (P=0.006), respectively. In addition, final body weight increased by 5.5% (P=0.001) in Trial 2 and production value improved by 6.8% (P=0.015) in Trial 1 by dietary DMG supplementation. Mortality in all trials was similar between dietary treatments. In all 3 trials, cold carcass weight and total meat yield were as well similar between broiler chickens fed the control and DMG diets. In Trial 1, dietary DMG had no effect on breast meat yield in male broiler chickens, but it increased breast meat yield in female broiler chickens (diet×sex, P=0.004). Organoleptic quality of roasted breast meat assessed only in Trial 2 was not affected by dietary treatments. In conclusion, dietary supplementation of DMG at 1g Na DMG/kg can considerably improve s production performance in broiler chickens.

Supplementation of guanidinoacetic acid to broiler diets: Effects on performance, carcass characteristics, meat quality, and energy metabolism

Creatine, (CREA) a central constituent in energy metabolism, is obtained from dietary animal protein or de novo synthesis from guanidinoacetic acid (GAA). Especially in all-vegetable diets, supplemental CREA or GAA may restore the CREA availability in tissues, and hence, improve performance. In this study, 768 one-d-old male Ross 308 broilers were assigned to 1 of 4 diets: negative control, all-vegetable corn-soybean-based; negative control supplemented with either 0.6 or 1.2 g of GAA per kilogram of feed; and positive control (60, 30, and 30 g/kg of fish meal in the starter, grower, and finisher diets, respectively). Each treatment was replicated in 6 pens of 32 birds each. At the end of the grower period (d 26), 2 birds per pen were euthanized for metabolic measurements. Four broilers per pen were selected at slaughter age (d 39) to determine carcass characteristics and meat quality. Compared with the negative control, GAA supplementation resulted in an improved gain:feed ratio (P < 0.05) and ADG (P < 0.05; + 2.7 and + 2.2% for GAA at 0.6 and 1.2 g/kg, respectively) throughout the entire period. Breast meat yield was higher for the GAA diets compared with that of the negative control birds (P < 0.05; 30.6 vs. 29.4%) and was comparable with that of the positive control birds (30.2%). With regard to meat quality, lower ultimate pH values, higher cooking and press fluid losses, and higher color L* values were observed for the GAA diets compared with those of the negative control diet (P < 0.05). These effects were small, however. The GAA and CREA levels in breast meat were lower and higher, respectively, in GAA-fed birds compared with those of the control birds (P < 0.01). The diets did not affect plasma metabolic traits, except that plasma insulin-like growth factor I concentrations were almost twice as high in animals fed 1.2 g/kg of GAA compared with those of all other treatments. The GAA included in all-vegetable diets improved animal performance for the whole rearing period and increased breast meat yield.

Modulation of glycogen and breast meat processing ability by nutrition in chickens: Effect of crude protein level in 2 chicken genotypes1

The aim of the study was to evaluate the impact of 2 isoenergetic growing diets with different CP (17 vs. 23%) on the performance and breast meat quality of 2 lines of chicken divergently selected for abdominal fatness [i.e., fat and lean (LL) lines]. Growth performance, breast and abdominal fat yields, breast meat quality parameters (pH, color, drip loss), and muscle glycogen storage at death were measured. Increased dietary CP resulted in increased BW, increased breast meat yield, and reduced abdominal fatness at slaughter regardless of genotype (P < 0.001). By contrast, dietary CP affected glycogen storage and the related meat quality parameters only in the LL chickens. Giving LL chickens the low-CP diet led to reduced concentration of muscle glycogen (P < 0.01), and as a result, breast meat with a higher (P < 0.001) ultimate pH, decreased (P < 0.001) lightness, and reduced (P < 0.001) drip loss during storage. The decreased muscle glycogen content observed in LL receiving the low-CP diet compared with the high-CP diet occurred concomitantly with greater phosphorylation amount for the α-catalytic subunit of adenosine monophosphate-activated protein kinase and glycogen synthase. This was consistent with the reduced muscle glycogen content observed in LL fed the low-CP diet because adenosine monophosphate-activated protein kinase inhibits glycogen synthesis through its action on glycogen synthase. Our results demonstrated that nutrition is an effective means of modulating breast meat properties in the chicken. The results also highlighted the need to take into account interaction with the genetic background of the animal to select nutritional strategies to improve meat quality traits in poultry.

High eggshell temperatures during incubation decrease growth performance and increase the incidence of ascites in broiler chickens

High eggshell temperatures (EST; ≥38.9°C) during the second half of incubation are known to decrease the body and organ development of broiler hatchlings. In particular, relative heart weights are decreased by a high EST, and this may increase the incidence of metabolic disorders that are associated with cardiovascular development, such as ascites. The current study investigated the effects of a high EST on chick quality, subsequent performance, and the incidence of ascites later in life. Eggs were incubated at a normal (37.8°C) or high (38.9°C) EST from d 7 of incubation onward. After hatching, the chickens were housed per EST in pens, and a normal or cold temperature schedule was applied during the grow-out period. Hatchability, hatchling quality, BW, feed conversion ratio, total mortality, mortality associated with ascites, slaughter characteristics, and ascites susceptibility at 6 wk of age were evaluated. Except for total ventricle weight, no interaction was found between EST and the grow-out temperature. Hatchability was comparable between the EST treatments, but the percentage of second-grade chickens was 0.7% higher at the high EST. Yolk-free body mass was 3.0 g lower, and heart weights were 26% lower at hatch in the high compared with the normal EST treatment. Body weight continued to be less during the grow-out period after the high EST incubation. However, breast meat yield was 1.0% higher in the high than in the normal EST. Feed conversion ratio did not differ between EST treatments. Total mortality was 4.1% higher and mortality associated with ascites was 3.8% higher in the high compared with the normal EST treatment. The ratio between the right and total ventricle was 1.1% higher in the high compared with the normal EST treatment at slaughter age. In conclusion, a high EST from d 7 of incubation onward decreased hatchling quality and growth performance, but increased breast meat yield. Furthermore, high EST incubation increased the incidence of ascites, which may be related to the reduced heart development at hatch.

Effects of dietary energy and protein dilution and time of feed replacement from starter to grower on broiler chickens performance

An experiment was conducted to study the effects of dietary energy and protein dilution and time of feed replacement from starter to grower on performance of broilers with a 2×3 factorial arrangement in a completely randomized design with 480 day-old broilers from 1-42 day of age. Experimental treatments were 5% energy and protein diluted diets and starter diet was fed to 7, 14 or 21 days and finisher diet was fed beginning at 35 days. Grower diet was fed for variable times depending upon termination of feeding starter diet and initiation of finisher diet. Dilution of both energy and protein had no (P>0.05) significant effect on chicks performance, but significantly (P<0.05) increased breast meat yield. Reduction the time of feeding starter diet did not show any significant effects on bird\'s performance. From 1-42 days of age, the interaction between dilution of both energy and protein and changing time from starter to grower diets on body weight and feed intake was not significant(P<0.05). The results from this study suggest that diluting of both energy and protein up to 5% from 1-42 days of age and decreasing the time of starter diet had no adverse effect on broiler chickens performance and it may be beneficial economically.

Broiler responses to reduced-protein diets supplemented with valine, isoleucine, glycine, and glutamic acid

SUMMARY Reduced performance is eventually observed when broilers are fed low-protein diets, even when industrial amino acids (AA) are provided to reach requirement levels. The reason for this detrimental effect has not been precisely determined, but it is possible that nonessential AA become limiting below a certain level of protein in the diet. The objective of this study was to evaluate the effects of Val, Ile, Gly, and Glu supplementation, individually or combined, in broiler diets with gradual reductions in protein. A total of 2,016 Ross × Ross 308 male broilers were fed 8 treatments with 9 replications (28 birds per pen) during a 42-d production period. overall care of birds complied with animal welfare directives from the Universidade Federal do Rio Grande do Sul. The control diet (treatment 1) was formulated without restricting CP, maintaining a Gly + Ser:Lys ratio of 155 or 158%. The other treatments, when not supplemented with l-Glu, had a CP content dependent on the fixed ratios of AA to Lys, generating diets with lower CP contents than the control diet. Treatment 2 was formulated with l-Val; treatment 3 with l-Val and Gly; treatment 4 with l-Val + l-Glu; treatment 5 with l-Val + Gly + l-Glu; treatment 6 with l-Val + l-Ile; treatment 7 with l-Val + l-Ile + Gly; and treatment 8 with l-Val + l-Ile + Gly + l-Glu. Dietary CP varied with feeding phase and treatment and reached 2.5% as the greatest reduction obtained. Supplementation of Gly and Glu improved BW gain and feed conversion. Benefits attributable to Gly supplementation were observed mainly in the early phases of growth. Conversely, broilers fed diets supplemented with Glu exhibited advantages in growth throughout experimentation. Addition of Ile, Glu, and Gly increased breast meat yield compared with broilers fed diets supplemented with only l-Val. Supplementation of Ile improved breast meat yield. Good broiler growth and meat yield can be obtained with Gly and Glu supplementation in reduced-CP diets, which implies a need for nitrogen for the synthesis of nonessential AA.

Increasing Dietary Lysine Increases Final pH and Decreases Drip Loss of Broiler Breast Meat

Responses to increased dietary Lys concentrations were evaluated on 1,584 Ross 308 male broilers between 21 and 42 d of age housed according to 2 bird densities. The experimental design was composed of 8 factorial treatments: 2 bird densities (22 or 44 broilers/ 1.7 m2 pen) × 4 true digestible (TD) Lys levels (0.83, 0.93, 1.03, and 1.13%). There were 6 repetitions per treatment. Birds were weighed individually at d 21 and 42. Feed consumption was recorded per pen. Body weight gain and feed conversion were calculated over the experimental period. Forty-eight broilers per treatment were dissected at 42 d of age. Final pH and drip loss during storage were measured on the pectoralis major. Density adversely affected feed intake (169 ± 1 and 160 ± 1 g/d with 22 and 44 birds per pen, respectively, P< 0.05), growth rate (97.4 ± 0.5 and 91.0 ± 0.7 g/d, P< 0.05), and feed conversion (1.730 ± 0.008 and 1.760 ± 0.006, P< 0.05). Except for feed intake, there was no interaction between the effects of bird density and dietary Lys. An increase in dietary TD Lys from 0.83 to 0.93% resulted in an increased growth rate (from 91.8 ± 1.6 to 95.5 ± 0.8 g/d, P< 0.05), improved feed conversion (from 1.783 ± 0.008 to 1.742 ± 0.009, P< 0.05), and increased breast meat yield (22.0 ± 0.1% to 22.7 ± 0.2%, P< 0.01). Performance and body composition traits were not significantly improved for concentrations of TD Lys higher than 0.93%. However, final breast pH increased from 0.83 up to 1.03% TD Lys in the diet (6.02 ± 0.01 vs. 5.91 ± 0.01, P< 0.05), and drip loss correlatively decreased (0.85 ± 0.03% vs. 1.10 ± 0.06, P< 0.05). This result opens new way of research for the definition of an amino acid requirement and on metabolic pathways involved in variations of breast muscle pH.

Decreasing Broiler Crude Protein Requirement by Methionine Supplementation

The experiment was conducted with two levels of protein (23 and 20% in starter, 20 and 18% in grower) and three levels of methionine (NRC, 110 of NRC and 120% of NRC in starter and grower stages). No significant differences were found for protein, methionine or their interaction on Feed Intake (FI) and Feed Conversion Ration (FCR) for starter and grower, with the exception of an interaction of 20% CP and 0.46% (120% ofNRC) methionine which significantly improved (p < 0.05) the FCR compared with 18% CP and 0.38% (NRC) level ofmethionone, at the grower stage. Carcass yield and breast meat were significantly (p < 0.05) increased by 23% Crude Protein (CP) compared to 20% in starter. In contrast, abdominal fat was significantly decreased (p < 0.05) by 23 and 20% CP diet in starter and grower, respectively compared to the other levels of CP as well as by high levels of methionine. In the interaction of 20% CP and high level of methionine (0.46%) on carcass yield, a significant increase (p < 0.05) was found in grower stage compared with 18% CP and both 0.38% and 0.42% (110% of NRC) of methionine levels. A similar effect was found on breast meat yield compared with interaction of both 0.5% (NRC) and 0.55% (110% of NRC) of methionine and 20% CP at 21 days, as well as at 42 days of age with 0.38% methionine and 18% CP. Finally, the results of this study, have suggested that methionine/CP ratio could be adjusted at 0.024% (0.024 g methionine/per g crude protein) in starter and 0.023% for grower. Decreased CP in the diet, increased breast meat yield and reduction of abdominal fat were achieved by these ratios of methionine/protein.

Growth Performance, Meat Yield, and Economic Responses of Broilers Provided Diets Varying in Amino Acid Density from Thirty-Six to Fifty-Nine Days of Age

Providing broilers diets formulated to a high amino acid density early in life improves subsequent growth performance and meat yield. Diets formulated to high amino acid concentrations beyond 5 wk of age may increase breast meat yield but may not be economically justified. This study examined growth, meat yield, and economic responses of broilers provided diets varying in amino acid density from 36 to 59 d of age. Birds were given a 4-phase feeding program: starter (1 to 17 d), grower (18 to 35 d), withdrawal-1 (WD1; 36 to 47 d), and withdrawal-2 (WD2; 48 to 59 d of age). All birds were fed a common, high amino acid density diet to 35 d of age (HH). Broilers were provided diets characterized as being high (H), moderate (M), or low (L) in amino acid density for the WD1 and WD2 periods. Dietary treatments were HHHH, HHHM, HHHL, HHMM, HHML, and HHLL from d 1 to 59, with H, M, and L representing the diets fed during each of the 4 periods (starter, grower, WD1 and WD2).Cumulative feed conversion was improved when the HHHH feeding regimen was fed, whereas other final live performance measurements were not affected. Decreasing amino acid density (HHLL and HHHL) limited yields of breast fillets, tenders, and total white meat when compared with the HHHH regimen. As amino acid density decreased from HHHH to HHHM, HHMM, and HHML, carcass yield and breast meat yield were not affected. In general, providing the HHHH feeding regimen increased economic gross feeding margin compared with the other dietary treatments.

Evaluation of sodium bicarbonate, chloride, or sulfate with a coccidiostat in corn-soy or corn-soy-meat diets for broiler chickens

During the period from January to June, combined-sex broiler chickens were inoculated with coccidia via drinking water at 14 d of age. In a completely randomized design (eight replicate pens; 88 chicks per pen) using built-up litter, experimental diets contained monensin plus 0.20% dietary sodium bicarbonate (SBC), which provided 0.054% sodium and 0.144% bicarbonate. Treatment with SBC significantly improved coccidial lesion score, 45-d body weight, and feed efficiency compared with monensin alone. In a 2 x 5 factorial trial using built-up litter pens (eight replicate pens; 88 chicks per pen) vs. each ionophore alone, 0.20% dietary SBC with monensin significantly improved body weight, uniformity, and feed efficiency; 0.20% SBC with halifuginone, lasalocid, monensin, or salinomycin significantly reduced mortality; and 0.20% SBC with lasalocid, monensin, or salinomycin significantly increased breast meat yield. In a 2x4 factorial trial (12 replicate pens; 88 chicks per pen) on built-up litter, corn-soy and corn-soy-meat diets (higher potassium, lower chloride) with monensin were evaluated using 0.054% sodium from SBC, NaCl, or sodium sulfate decahydrate (SSD). With both diet types, SBC (0.20%) or NaCl (0.139% extra) significantly improved weight uniformity, feed efficiency, mortality, and breast meat yield; however, the SSD results were closer to controls. In a 21-d battery brooder test using similar diets and design (2x4 factorial; 4 replicate pens; 10 chicks per pen), SBC and NaCl significantly reduced coccidial lesion scores; SSD produced a significant, but weaker effect. Extra NaCl significantly increased water intake (approximately 37%), water excretion (approximately 27%), and litter moisture (approximately 22%) with both diet types. The SSD did not affect water intake.

Dietary supplements of methionine increase breast meat yield and decrease abdominal fat in growing broiler chickens

The response of male broiler chickens to graded amounts of an essential amino acid (methionine) or an amino acid analogue (methionine hydroxy analogue free acid, MHA-FA) was examined in this experiment. The effects of each supplement on food intake, food conversion and the masses of a demand tissue (breast meat) and an indicator of body fat (abdominal fat pad) were measured. Birds grew significantly faster, ate more and had a lower food conversion ratio when there was more DL-methionine or MHA-FA in the diet. After standardising the differences in food intake between treatments, there were still highly significant differences in liveweight between diets. After removing the variation due to treatment differences in body mass, the data showed that adding either DL-methionine or MHA-FA to the diet increased the mass of breast meat and reduced the size of the abdominal fat pad. Exponential equations fitted to the body mass and feed conversion ratio data indicate that, in an equimolar comparison, MHA-FA is 78 and 70% as potent as DL-methionine for growth and feed conversion ratio respectively. Similar equations fitted to the carcass data show that MHA-FA is only 71% as potent as DL-methionine in depositing breast tissue. Increasing amounts of DL-methionine reduced the variability in liveweight and carcass, breast and abdominal fat pad weights. Adding 0.05% MHA-FA reduced variability in these traits compared with the basal ration but higher amounts of MHA-FA had no additional effect.

Broiler Response to Friction Compacting of Feed

Friction compacting is a relatively new milling technology that preconditions feed for pelleting, using higher temperatures and pressure than conventional steam conditioning. Four trials were conducted with male broiler chickens to 49 days of age using pelleted or compacted pelleted feeds. In all trials there was increase in body weight of broilers fed compacted diets at the end of the 17- to 21-day starter period, with this effect being significant (P < .05) in two of the trials. However, this effect was lost over time, and an all trials there was no diet effect on either 49-day body weight or feed efficiency. The same general effects were seen in diets composed essentially of corn and soybean, those containing more by-product ingredients, and diets of lower nutrient density. There is a slight indication of increased breast meat yield in birds fed compacted feeds.

Influence of dietary lysine levels and arginine:lysine ratios on performance of broilers exposed to heat or cold stress during the period of three to six weeks of age

Four trials of identical experimental design were conducted to determine the effects of temperature, dietary Lys level, and dietary Arg:Lys ratios on performance and carcass yield of male broilers. Birds of a commercial strain were grown from 21 to 42 d of age in wire-floored finishing batteries placed in environmental chambers. The chambers were programmed to provide either a constant thermoneutral temperature (21.1 C), a constant cold temperature (15.5 C), or a cycling hot diurnal temperature (25.5 to 33.3 C). Within each environment there was a factorial arrangement of three Lys levels (1.0, 1.1, and 1.2%) with four Arg:Lys ratios (1.1:1, 1.2:1, 1.3:1, and 1.4:1). Environmental temperature significantly influenced virtually every characteristic examined. Hot cyclic temperatures reduced weight gain, feed intake, and breast meat yield, and increased feed conversion, dressing percentage, leg quarter yield, and abdominal fat content. The cold environment promoted increased feed intake and mortality. Ascites and cardiomyopathy were the leading causes of death under cold exposure and thermoneutral conditions, whereas complications arising from heat exposure were the main cause of death under hot cyclic conditions. Levels of Lys affected leg quarter yield and abdominal fat content over all environments but increased breast meat yield only under cold conditions. Increasing Arg:Lys ratios improved feed conversion and dressing percentage and reduced abdominal fat content; it could not be determined whether these responses were consistent with Arg per se or were due to a nonspecific N response. As increasing Lys levels or Arg:Lys ratios did not improve weight gain, increase breast meat yield, or attenuate adverse effects due to heat or cold exposure, it is concluded that the levels of Lys and Arg suggested for 21 to 42 d by the NRC are adequate for birds of this age under the environmental conditions encountered.